**3. Structure of lignohemicellulosic biomass**

social fairness. There are gladness and sadness criticisms from both sugar mills entrepreneurs and capitalism lovers versus poorer workers at cane plantations, respectively. Let us emphasize the thoughts and opinions from the closer national teacher and researcher on environmental sciences, recalled his graduation title as a social scientist, too—Prof. Dr. Valdir Fernandes [10]. His comments and Strengths, Weaknesses Opportunities, Threats (SWOT) guidelines were built in a partnership with other three other publication colleagues and was

(a) Brazil is committed from many decades ago with sugarcane ethanol as a mandatory surrogate for petrochemical derived fuels; (b) given the huge figures for production and processing, when examining the sustainability, it is necessary to build tools which allow to assess an integrated conception of the sugarcane matter, prospects, goals and subjects, about everything to help and to influence decision-makers to establish public policies for a sustainable development; (c) the complexity may be captured from economic and social indicators without no reduction in the significance of each system component; (d) taking the State of São Paulo—the major Brazilian producer and more developed state federation unit—and the trustable indicators raised by its Environmental Secretariat—sounded as one pertinent strategy for the current evaluation; (e) water supply and its quality regarding environmental implications is a valuable cornerstone; (f) the evaluation of environmental indicators encompasses the application of extensive interviews allied to experts workshop pointing out to a set of benchmarks; in the present case, 16 respectable experts were involved. These interviews established three main focus: water, soil and atmosphere. Each focus considering, respectively, 11, 12 and 2 relevant aspects/opinions input. As illustrative examples, reduce availability, oxygen-deprivation as biochemical oxygen demand (BOD) and chemical oxygen demand (COD) parameters, eutrophication of surface sheets by NPK and respective leaching intensity in the case of water, loss of soil nutrients nitrification and acidification by low-pH vinasse, microbiota flora reduction for the soil focus and some possibly unchanged/ unchangeable indicators such as photochemical formation of tropospheric ozone and atmospheric acidification (permanent greenhouse gases release). Discussions and conclusions drawn for other mentioned topics in water and soil derived from the expert's team suggested opinions and additions. A strengths /weaknesses/opportunities and threats, namely, a SWOT analysis was built. (g) conclusively, a better guide for the people taking decisions sugarcane industrial managers, union leaders, politicians, governmental authorities in agricultural, health, economic and social fields—all them committed with the whole society benefits on safety, welfare and progress—is to consider and refine, *inter allia*, environmental indicators to feed the discussion and legal decisions to support the so needed sustainability

To the authors understanding this remarkable contribution of this environmentally proactive scientists quartet from USP—University of São Paulo, UTFPR—Federal Technological University of Paraná and UFPE—Federal University of Pernambuco (prudly and proudly Brazilian scientists!) deserves a complete reading of their corresponding 27 pages full report for any reader interested in the profits and negative implications of any giant agribusiness as well as other related industrial and highly polluting factories on commodities (e.g., pulp/

summarized below:

244 Sugarcane - Technology and Research

in the giant sugarcane business.

paper, timber/saw mills).

Cellulosic materials are the most abundant renewable polymer resource available in nature as the main component of plant cell walls, which in turn is subdivided into primary wall and secondary parts. Unlike other homopolysaccharides encountered anywhere, cellulose occurs in close association with hemicelluloses and lignin, then named ligno(hemi)cellulose or shortly, L(h)C (**Figure 1**). Together, these three biomolecules are the main components of plant biomasses corresponding, respectively, as 40–60% for cellulose, 20–40% for hemicelluloses and 10–25% for lignin in any L(h)C biomass [11]. The distribution of cellulose, hemicelluloses and lignin varies considerably among cell wall layers. L(h)C biomass also can contain some pectin and xyloglucan along with minor amounts of minerals (ash) and various other compounds, which are called extractives.

Exceptions for this statement seldom occur in the plant kingdom but is the case of cotton caps and kapok ripen fruits where cellulose fibers are almost pure, meaning free of hemicellulose and lignin. Mention to some polysaccharide bacterial anabolism is mandatory here: some species of acetogenic bacteria, specially species such as *Gluconacetobacter xylinus*, formerly known as *Acetobacter xylinum* and since reclassified as *Komagataeibacter xylinus* [12], biosynthesize effectively pure cellulose ribbons of special architecture as soft biofilm gels. There are now a plenty of medical and other biotechnological applications for this noble cellulose occurrence and intensive production.

Southeastern Asian countries (Thailand, Malaysia, the Philippines and Indonesia) consume it as appreciated food known as "nata-de-coco". We have been consolidating other biotech products, one of them its covalently died derivative (Remazol Brilliant Blue R (RBB)-bacterial cellulose) for cellulolytic enzymes detection and measuring [13], following our pioneering

**Figure 1.** General ligno(hemi)cellulose structure of the plant cell wall.

report of its application just after a quick cleanliness for entrapped cells (although known as Generally Recognized as Safe-GRAS bacterium) as a temporary skin substitute in the case of human skin burns and other dermal injuries [14].

Cellulose consists of a collection of linear chains of *β*-(1,4)-linked D-glucopyranosyl units. L(h) C biomass include agricultural and agroindustrial residues (cane bagasse, cereal straws, cornstover, cobs or husk and similar polysaccharide-rich materials); wood materials (branches, bark, stumps, wood wastes from sawmills and paper mills) and dedicated energy crops (*Miscanthus* sp., switchgrass, etc.) including energy cane, a hybrid lineage of sugarcane that has been bred and selected for fiber production over sucrose production. In Brazil, pioneer hybrids of energy cane were produced by CANAVIALIS, a private sugarcane breeding company that obtained 138% more total biomass (green matter) per area than a good conventional sugarcane variety and 235% more fiber [15].

The cellulose chains are packed in layers that interact with each other by van der Waals forces with intramolecular and intermolecular hydrogen bonds to form microfibrils [16, 17]. Because of these interactions, cellulose has a recalcitrant crystalline nature that makes it generally resistant to degradation by any mold or bacterial cellulose complexes (endoglucanases + cellobiohydrolases I and II and *β*-glucosidases). However, some reports have shown that a class of oxidative enzymes, the lytic polysaccharide monoxygenases, have the capacity to degrade recalcitrant crystalline cell wall components, including cellulose [18, 19]. This is, undoubtly, a remarkable progress in biochemical technology.

called middle lamella that acts like a cementing agent biding primary cell walls together. Lignin also provides rigidity, enhances mechanical strength, reinforce vascular cells and acts as a pathogen and water-impermeable barrier for the plant tissue [22]. Lignin is built from monolignols based on three monomeric precursors (coniferyl, sinapyl and *p*-coumaryl alcohols) which appear to be incorporated into the lignin polymer in a non-predictable way [23]. It is worth to mention that oppositely to hemicelluloses (in fact always heteropolysaccharides) with a plenty of secondary substituents and also displaying a covalent connection with part of lignin, cellulose is a pure homopoly-*β*-glucan. Its interaction with other polymers are solely

Sugar Versatility—Chemical and Bioprocessing of Many Phytobiomass Polysaccharides Using…

http://dx.doi.org/10.5772/intechopen.75229

247

**Table 1.** Biomass composition in common L(h)C feedstocks (source: Adapted from [24]).

A determining factor when selecting biomass for biochemical processing to recover their respective sugars is the different physico-chemical properties of various L(h)C materials, what is based, at first glance, in their major chemical composition. **Table 1** presents how L(h) C can be diverse depending on the origin and part of the plant. As the enzymatic, or even chemical hydrolysis of cellulose is greater than that of lignin, the complete conversion of the carbon-containing plant material present as cellulose is greater for plants with a lower pro-

L(h)C biomass, as said before, can be obtained at relatively low cost in different forms, representing a potential sugar source for the fermentative production of renewable fuels as well as other materials in modern biorefineries. Most of these potential applications rely on the predominant cellulose fraction susceptibility to enzymatic hydrolysis/acid hydrolyses or other

However, the intrinsic nature of L(h)C materials is completely different from that found in starch. Starch granule serve as a temporary energy storage polymer with glycosidic linkages that can be readily hydrolyzed to supply glucose for germination and plant growth.

based on physical rather than chemical linkages.

**4. L(h)C biomass deconstruction to sugars**

portion of lignin.

structural changes.

Hemicelluloses are a diverse group of polysaccharides generally characterized by having a *β*-(1,4)-linked sugar backbone with the main function to reinforce the cell wall by interaction with cellulose and lignin. In xylans (angiosperms or hardwood and grasses), mannans (conifers and hardwoods) and xyloglucans (predominant in the primary bed of dicot and monocot/ non-gramineous monocot cell walls), the backbone sugars are *β*-1,4-d-Xyl, *β*-1,4-d-Man, and *β*-1,4-d-Glc, respectively, while in glucomannans, the backbone comprises of randomly distributed *β*-1,4-d-Man > *β*-1,4- d-Glc units [20]. Xylans are the major constituent in secondary plant cell wall comprising a backbone of repeating *β*-(1,4)-d-Xyl residues most often substituted by L-arabinosyl (Ara*f*) and D-glucuronic acid (GlcpA)/4-O-Methyl-D-glucuronic residues. O-acetyl substituents are also present in the main xylopyranosyl units.

The L-arabinofuranosyl residues can contain ferulic acid groups esterified to the O-5 position of the carboxyl group which in turn can be oxidatively cross-linked to lignin incorporating xylans into the lignin reinforcing even more the network [21]. This feature particularly explains why rye bread hardens as compared with the softer wheat bread. Softwoods and hardwoods can have different hemicellulose content [22]. Hardwood hemicelluloses are composed typically by highly acetylated heteroxylans (4-O-methyl glucuronoxylans) with low amounts glucomannans. Instead, softwoods are common in the presence of partly acetylated galactoglucomannans and glucomannans with xylans corresponding to a minor fraction of their hemicellulose content [22].

Lignin is a phenolic polymer mainly deposited in secondary cell wall coating cellulose and generally combined with hemicelluloses, and built up almost entirely an intervening layer Sugar Versatility—Chemical and Bioprocessing of Many Phytobiomass Polysaccharides Using… http://dx.doi.org/10.5772/intechopen.75229 247


**Table 1.** Biomass composition in common L(h)C feedstocks (source: Adapted from [24]).

report of its application just after a quick cleanliness for entrapped cells (although known as Generally Recognized as Safe-GRAS bacterium) as a temporary skin substitute in the case of

Cellulose consists of a collection of linear chains of *β*-(1,4)-linked D-glucopyranosyl units. L(h) C biomass include agricultural and agroindustrial residues (cane bagasse, cereal straws, cornstover, cobs or husk and similar polysaccharide-rich materials); wood materials (branches, bark, stumps, wood wastes from sawmills and paper mills) and dedicated energy crops (*Miscanthus* sp., switchgrass, etc.) including energy cane, a hybrid lineage of sugarcane that has been bred and selected for fiber production over sucrose production. In Brazil, pioneer hybrids of energy cane were produced by CANAVIALIS, a private sugarcane breeding company that obtained 138% more total biomass (green matter) per area than a good conventional

The cellulose chains are packed in layers that interact with each other by van der Waals forces with intramolecular and intermolecular hydrogen bonds to form microfibrils [16, 17]. Because of these interactions, cellulose has a recalcitrant crystalline nature that makes it generally resistant to degradation by any mold or bacterial cellulose complexes (endoglucanases + cellobiohydrolases I and II and *β*-glucosidases). However, some reports have shown that a class of oxidative enzymes, the lytic polysaccharide monoxygenases, have the capacity to degrade recalcitrant crystalline cell wall components, including cellulose [18, 19]. This is, undoubtly, a

Hemicelluloses are a diverse group of polysaccharides generally characterized by having a *β*-(1,4)-linked sugar backbone with the main function to reinforce the cell wall by interaction with cellulose and lignin. In xylans (angiosperms or hardwood and grasses), mannans (conifers and hardwoods) and xyloglucans (predominant in the primary bed of dicot and monocot/ non-gramineous monocot cell walls), the backbone sugars are *β*-1,4-d-Xyl, *β*-1,4-d-Man, and *β*-1,4-d-Glc, respectively, while in glucomannans, the backbone comprises of randomly distributed *β*-1,4-d-Man > *β*-1,4- d-Glc units [20]. Xylans are the major constituent in secondary plant cell wall comprising a backbone of repeating *β*-(1,4)-d-Xyl residues most often substituted by L-arabinosyl (Ara*f*) and D-glucuronic acid (GlcpA)/4-O-Methyl-D-glucuronic resi-

The L-arabinofuranosyl residues can contain ferulic acid groups esterified to the O-5 position of the carboxyl group which in turn can be oxidatively cross-linked to lignin incorporating xylans into the lignin reinforcing even more the network [21]. This feature particularly explains why rye bread hardens as compared with the softer wheat bread. Softwoods and hardwoods can have different hemicellulose content [22]. Hardwood hemicelluloses are composed typically by highly acetylated heteroxylans (4-O-methyl glucuronoxylans) with low amounts glucomannans. Instead, softwoods are common in the presence of partly acetylated galactoglucomannans and glucomannans with xylans corresponding to a minor fraction of

Lignin is a phenolic polymer mainly deposited in secondary cell wall coating cellulose and generally combined with hemicelluloses, and built up almost entirely an intervening layer

dues. O-acetyl substituents are also present in the main xylopyranosyl units.

human skin burns and other dermal injuries [14].

246 Sugarcane - Technology and Research

sugarcane variety and 235% more fiber [15].

remarkable progress in biochemical technology.

their hemicellulose content [22].

called middle lamella that acts like a cementing agent biding primary cell walls together. Lignin also provides rigidity, enhances mechanical strength, reinforce vascular cells and acts as a pathogen and water-impermeable barrier for the plant tissue [22]. Lignin is built from monolignols based on three monomeric precursors (coniferyl, sinapyl and *p*-coumaryl alcohols) which appear to be incorporated into the lignin polymer in a non-predictable way [23].

It is worth to mention that oppositely to hemicelluloses (in fact always heteropolysaccharides) with a plenty of secondary substituents and also displaying a covalent connection with part of lignin, cellulose is a pure homopoly-*β*-glucan. Its interaction with other polymers are solely based on physical rather than chemical linkages.

A determining factor when selecting biomass for biochemical processing to recover their respective sugars is the different physico-chemical properties of various L(h)C materials, what is based, at first glance, in their major chemical composition. **Table 1** presents how L(h) C can be diverse depending on the origin and part of the plant. As the enzymatic, or even chemical hydrolysis of cellulose is greater than that of lignin, the complete conversion of the carbon-containing plant material present as cellulose is greater for plants with a lower proportion of lignin.
